1. Field of the Invention
The present invention relates to a driving circuit for a light-emitting diode (LED) lamp. More particularly, the present invention relates to a driving circuit for a single-string LED lamp including a plurality LEDs all coupled in series.
2. Description of the Related Art
Liquid crystal displays (LCDs) such as LCD monitors, LCD television and all-in-one computers already use LED lamps as backlight sources. The LED lamp includes a plurality of LEDs coupled in series and/or parallel, such as eight parallel strings of ten LEDs coupled in series. A driving circuit for the LED lamp converts an input low DC voltage (such as 12-19V) to a high DC voltage (such as 30V-60V) to provide a supply voltage to drive the LED lamp, in which the supply voltage value is determined by the number of the LEDs of each string.
Presently, the LED lamp usually uses multiple parallel strings such as four, six, eight parallel strings and so on. To balance current flowing through each string, the driving circuit has to use a specific-purpose integrated circuit (IC) having current balance function or a complex current balance circuit, increasing the design cost of the driving circuit. Moreover, LED lamps fabricated by different manufacturers or even by the same manufacturer have different input/output terminal designs and include different numbers of parallel strings, so that it is impossible to provide the standardization design for connectors of the driving circuit used to connect to the LED lamp. Thus, the driving circuit for one LED lamp cannot be used for another LED lamp, wasting human resources on the designs of the driving circuits for different LED lamps.